1. Field of the Invention
The present invention relates to a plasma enhanced CVD apparatus equipped with a plasma generating electrode in a processing chamber, and further, relates to plasma enhanced CVD in which a conductive film is deposited by using the plasma enhanced CVD apparatus. Moreover, the present invention relates to a plasma processing apparatus equipped with a plasma generating electrode in a processing chamber.
2. Description of the Related Art
Plasma enhanced CVD is a method of depositing thin films on substrates by utilizing the chemical reaction of source gases. This method has been widely applied to depositing thin films, such as metallic films, semiconductor films, insulating films, photoconductive films, barrier films, and adhesion films, which films are used for semiconductor integrated circuits, superconductive devices, various kinds of electronic devices, and various kinds of sensors. In general, plasma generating electrodes are employed for generating plasma in processing chambers, and typically, radio-frequency powered electrodes are used. The systems of plasma generating electrodes are classified as a capacitively coupling system and an inductively coupling system. They can also be classified as an external electrode system in which an electrode is provided outside of the processing chamber and an internal electrode system in which an electrode is positioned inside of a processing chamber. Parallel-plate plasma enhanced CVD apparatuses according to the capacitively coupling system and the internal electrode system are most widely used among these. In addition, among plasma enhanced CVD apparatuses according the inductively coupling system and the external electrode system, apparatuses are frequently used that are provided with coiled electrodes winding around discharge chambers made of quartz glass. The present invention relates to a plasma enhanced CVD apparatus according to the internal electrode system, and further, the present invention relates to deposition of conductive films using this plasma enhanced CVD apparatus.
In a plasma enhanced CVD apparatus according to the internal electrode system, a plasma generating electrode, to which a radio frequency power is applied, is introduced into a processing chamber through a wall thereof. At each of the sites introducing the electrode, an electrical insulation member is inserted between the plasma generating electrode and the grounded metallic processing chamber so as to electrically insulate them.
The following problems appear when a conductive film is deposited on a substrate using the foregoing plasma enhanced CVD apparatus of the internal electrode system: If a conductive film adheres to the afore-mentioned electrical insulation members, the insulation performance thereof deteriorates, thus impairing stable plasma generation. Therefore, it is necessary to specially design the plasma generating electrode or surrounding structures thereof to prevent the conductive film from adhering to the electrical insulation members. In the case of a parallel-plate plasma enhanced CVD apparatus, plasma is generated between the parallel electrodes facing each other, therefore the conductive film does not easily adhere to the electrical insulation members arranged at the back sides of the parallel electrodes. Meanwhile, if an internal electrode (a coiled electrode) according to the inductively coupling system is used, plasma is generated around the plasma generating electrode, thus the electrical insulation member is readily exposed to the plasma and the conductive film easily adheres thereto.
Regarding these problems, Japanese Patent Publication No. 60-7937 discloses a technique, in which grooves are formed in electrical insulation members for avoiding degradation of insulation due to the conductive-film adhesion. This technique relates to an insulating spacer inserted between a pair of parallel electrodes facing each other in a processing chamber, in which a groove is formed in the insulating spacer to avoid degradation of insulation due to conductive-film adhesion.
Further, Japanese Patent Laid-Open No. 7-18433 discloses an apparatus for sputtering by using an internal electrode according to the inductively coupling system. Although this technique describes an insulation portion introducing the internal electrode into a vacuum chamber arranged in the dead zone of the chamber so as to prevent metallic films from depositing on the insulation portion, a practical shape or positioning of the insulation portion is not disclosed.
The foregoing problems are overcome if the conductive films are deposited according to the external electrode system. Other problems however may occur as follows: For example, when a coiled electrode winding around a discharge chamber made of quartz glass is used for generating plasma, conductive films are deposited on the inner walls of the discharge chamber. As a result, the conductive films shield the radio-frequency power applied to the coiled electrode. The plasma generated in the discharge chamber thereby becomes unstable, and further, in the worst case plasma generation per se becomes impossible. Therefore, frequent cleaning is required for the inner walls of the discharge chamber in the case of depositing conductive films on a substrate using a conventional plasma enhanced CVD apparatus according to the external electrode system.
An object of the present invention is to maintain stable plasma over a long period of time by avoiding a decrease in insulation performance between a plasma generating electrode and a processing chamber during deposition of conductive films on a substrate in a plasma enhanced CVD apparatus equipped with the plasma generating electrode in the processing chamber.